As working machines, various types of construction machine are known, such as for example hydraulic shovels and wheel loaders and the like, as well as haulage vehicles and the like such as dump trucks and so on. These working machines can easily become objects of theft, since they are of comparatively high price, and since moreover they are often used at workplaces which are far from human habitation.
Accordingly, a theft prevention technique has been proposed (in Patent Document #1), in which it is arranged to permit starting of the engine, only if a region in which the working machine can be used is set up in advance, and if moreover the user has inputted a predetermined secret security number to the working machine.    Patent Document #1: Japanese Laid-Open Patent Publication 2004-114893.